Handrail

Abstract: Background. An inability to negotiate stairs is a marker of disability and functional decline and can be a critical factor in loss of independence in older people. There is limited research on the underlying factors that impair performance in this important activity of daily living. We examined which physical and psychological factors are associated with stair climbing and stair descending performance in older people. Methods. Six hundred sixty-four community-dwelling people aged 75–98 years (mean age ¼ 80.1 years, standard deviation (SD) ¼ 4.4 years) underwent stair negotiation tests as well as tests of lower limb strength, vision, peripheral sensation, reaction time, and balance and completed questionnaires measuring psychological and health status. Results. Many physiological and psychological factors were significantly associated with stair negotiation speed. Multiple regression analyses revealed that knee extension and knee flexor strength, lower limb proprioception, edge contrast sensitivity, reaction time involving a foot-press response, leaning balance, fear of falling, and the Short-Form 12 Health Status Questionnaire (SF-12) pain and vitality scores were significant and independent predictors of stair ascent and descent performance. The combined set of variables explained 47% of the variance in stair ascent performance and 50% of the variance in stair descent performance. Measures of strength, balance, vision, fear, and vitality also significantly discriminated between persons who did and did not require the use of the handrail when performing the tests. Discussion. In community-dwelling older people, impaired stair negotiation is associated not only with reduced strength but also with impaired sensation, strength, and balance; reduced vitality; presence of pain; and increased fear of falling.

Abstract: Objectives: To examine specific behaviors used by older adults while ascending and descending stairs and to assess the relationships between confidence and stair performance. Design: Cross-sectional. Setting: Center for Locomotion Studies, The Pennsylvania State University. Participants: Sixteen male (mean age=82.7, range= 77–89) and 16 female (mean age=82.2, range=77–87) community-dwelling adults. Measurements: A stair self-efficacy (SSE) test was created to assess individuals' confidence in their safety on stairs. Observational stair performance measures, measures of walking speed on stairs, and the total SSE score were examined for differences due to sex, and the relationships between SSE and specific stair behaviors were assessed. Results: There was a significant relationship between SSE and the safety precautions taken during stair negotiation. Those with lower SSE were more likely to ascend and descend the stairs at a slower speed, use the handrail to a greater extent, and position themselves closer to the rail. The women had lower domain-specific SSE and tended to use the handrail to a greater extent than men even though there were no sex differences in self-reported functional ability or general falls and mobility confidence. A small group of subjects exhibited characteristics of instability, particularly during stair descent, yet most of this group had high SSE scores and failed to use the handrail. Conclusion: It appears that confidence related to stair negotiation plays a major role in determining risk-taking propensity during stair use in older adults.

Abstract: This paper presents a biped humanoid robot that is able to walk on a rough terrain while touching a handrail. The contact wrench sum (CWS for short) is used as the criterion to judge if the contact between the robot and the environment is strongly stable under the sufficient friction assumption, where the contact points are not coplanar and the normal vectors at the points are not identical. It is confirmed that the proposed pattern generator can make the robot walk as desired in dynamics simulations and experiments, and the motions can be improved by a hand position control and using waist joints.

Abstract: The ability to reach and "grasp" (grip or touch) structures for support in reaction to instability is an important element of the postural repertoire. It is unclear, however, how the central nervous system (CNS) resolves the potential conflict between holding an object and the need to release the held object and grasp alternative support, particularly if the held object is perceived to be relevant to the task of stabilizing the body, e.g. an assistive device. This study examined whether compensatory grasping is inhibited when holding an object, and whether the influence differs when holding an assistive device (cane) versus a task-irrelevant object (top handle portion of a cane). We also investigated the influence of preloading the assistive device, to determine whether conflicting demands for arm-muscle activation (requiring disengagement of ongoing agonist or antagonist activity) would influence the inhibition of compensatory grasping. Unpredictable forward and backward platform translations were used to evoke the balancing reactions in 16 healthy young adults. A handrail was mounted to the right and foot motion was constrained by barriers, with the intent that successful balance recovery would (in large-perturbation trials) require subjects to release the held object and contact the rail with the right hand. Results showed that grasping reactions were commonly used to recover equilibrium when the hand was free (rail contact in 71% of large-perturbation trials). However, holding either the cane or canetop had a potent modulating effect: although early biceps activation was almost never inhibited completely (significant activity within 200 ms in 98% of trials), the average activation amplitude was attenuated by 30-64% and the average frequency of handrail contact was reduced by a factor of two or more. This reduced use of the rail occurred even though the consequence often involved falling against a safety harness or barriers. Handrail contact occurred least frequently when holding the cane during forward loss of balance: subjects persisted in pushing on the cane (failing to use the rail) in 93% of trials, even when the perturbations were too large to allow this strategy to be successful. Prior contraction (preloading the cane) did not influence any of these findings. Complex strategies (e.g. partial release of object) were often adopted to allow balance to be recovered without dropping the held object. Remarkably, it appears that the CNS may give priority to the ongoing task of holding an object, even when it has no stabilizing value (cane during backward falls) or any intrinsic value whatsoever (canetop).